The present invention relates to a water soluble dyestuff for inkjet recording and an aqueous inkjet recording liquid using the same. More specifically, it relates to a metal chelated dyestuff comprising a water soluble azo metal chelated compound suitable for inkjet recording and an aqueous inkjet recording liquid using the same.
The recording by blowing drops of recording liquid containing a water soluble dye such as a direct dye or an acid dye from a minute orifice, so-called inkjet recording method has been practically used.
With regard to the recording liquid, it is required to exhibit fast fixing to a recording paper widely used at general office work such as a paper for PPC (plain paper copier), i.e., a paper for electrophotography, fanhold paper (a continuous paper for computer, etc.), or the like, and also a good print quality of a printed matter, that is, no blotting and a clear outline. In addition, it is necessary to be excellent in stability during storage as a recording liquid. Therefore, the solvents which are possible to use are strictly limited.
With regard to the dye for the recording liquid, it is required that it has a sufficient solubility for the above limited solvents, and, in addition, is stable as a recording liquid even when it has been stored for a long period of time, and a printed image has high saturation and density, as well as the dye is excellent in water resistance, light resistance and indoor discoloring and fading property.
On the other hand, for forming a full color image in the inkjet recording method, using inks of three primary colors of yellow (Y), magenta (M) and cyan (C) or four colors wherein black (B) is additionally used, an image is formed by controlling the discharging amount of each ink through the mixing of these colors on a material to be recorded. Furthermore, at the formation of a full color image, it is necessary to express not only difference of colors but also shade of colors. The shade part is usually formed by the use of two or more inks different in concentration of dyestuff.
However, with regard to the conventional dyestuffs for inkjet, there is a problem of fading of an image caused by light irradiation, that is, a poor light resistance. In particular, it is a problem that a pale color part where an ink low in concentration of dyestuff is used exhibits a poor light resistance. Thus, it is desired to develop a dyestuff for inkjet which satisfies these many requirements at the same time.
In particular, as the magenta dyestuff to be used in the recording liquid, a metal-free direct dye (C.I. DR-227) and an acid dye (C.I. AR-249) which are commercially available dyes are hitherto employed (by the way, xe2x80x9cC.I.xe2x80x9d means xe2x80x9cColor Indexxe2x80x9d, xe2x80x9cARxe2x80x9d means xe2x80x9cAcid Redxe2x80x9d, and xe2x80x9cDRxe2x80x9d means xe2x80x9cDirect Redxe2x80x9d.).
A direct dye is unclear in color tone, but an acid dye showing a clear color tone tends to exhibit an inferior light resistance. Moreover, heretofore, a metal-containing azo dye has a good light resistance but exhibits a somber color tone and poor clearness. Therefore, it is desired to develop a dyestuff for inkjet which satisfies both of the color tone and light resistance.
Japanese Patent Laid-Open No. 42775/1982 discloses an aqueous ink for inkjet printing wherein at least one kind of 5-hydroxypyrazole azo dye having an azo group at the 4-position or complex salt dye thereof with copper, nickel or cobalt. However, the bonding position of the pyrazole ring to the azo group of the dye described therein is different from that in the general formula (1) of the invention.
Japanese Patent Laid-Open No. 259331/1998 discloses an aqueous inkjet recording liquid which contains a water soluble metal complex formed from a benzene azo compound and at least one kind of metal selected from nickel, cobalt, chromium or copper. However, the metal complex is different from the compound of the general formula (1) of the invention in view that the complex does not have a naphthalene ring.
Japanese Patent Laid-Open No. 140367/1999 discloses an ink composition containing a magenta dye ligand of 4-hydroxy-3-(2xe2x80x2-pyridylazo)-1-(sulfo substituted)naphthalene which coordinates to a polyvalent metal ion, and an ink vehicle. However, there is a difference in view that the compound of the general formula (1) of the invention is an azo compound having no pyridine ring.
These dyestuffs described in the known literatures not always satisfy the properties required for the dyestuff for inkjet printing such as clearness of color tone, light resistance, indoor discoloring and fading property, solubility, storage stability, and the like, sufficiently.
An object of the invention is to provide a water soluble dyestuff for inkjet printing which result in a good print quality even at printing on a plain paper and also a clear color tone with a high density, an excellent light resistance, small indoor discoloring and fading of a printed image, and exhibits a good solubility or stability during a long time storage of the dyestuff, and an aqueous inkjet printing liquid using the same.
The present inventors have achieved the above object by the use of a water soluble dyestuff which is an azo chelated compound of a specific azo compound with a metal element.
Namely, the gist of the invention is a metal chelated dyestuff for inkjet recording which is a water soluble azo metal chelated compound formed from an azo compound represented by the following general formula (1) and a metal element, and an aqueous ink jet recording liquid which contains at least one kind of the dyestuff selected from the metal chelated dyestuff and an aqueous medium. 
(where general formula (1) represents an azo dyestuff compound having at least one or more hydrophilic group in a molecule, X1 represents plural atoms required for forming at least one 5- to 7-membered heterocyclic ring, the heterocyclic ring containing X1 being a heterocyclic ring other than pyridine ring. The heterocyclic ring containing X1 may have substituent(s) on the heterocyclic ring, the substituent(s) on the heterocyclic ring may form a condensed ring through further condensation. The condensed heterocyclic ring containing X1 may be substituted. Ar1 represents a naphthyl group represented by the following general formulae (2)-(4). Y1 represents a chelating group, Z1 represents any substituent which may be different from each other, and a represents an integer of 0 to 6.) 
The following will explain the present invention in detail.
The metal chelated dyestuff of the invention is a water soluble azo metal chelated compound formed from an azo compound represented by the above general formula (1) and a metal element.
X1 represents two or more atoms necessary for forming at least one 5- to 7-membered heterocyclic ring but the heterocyclic ring containing X1 is a heterocyclic ring other than pyridine ring. The heterocyclic ring containing X1 is preferably imidazole ring, pyrazole ring, isoxazole ring, thiazole ring, thiadiazole ring, pyridazine ring, pyrimidine ring, pyrazine ring, benzothiazole ring, benzoxazole ring, or benzimidazole ring. Among them, it is preferred that the heterocyclic ring containing X1 is imidazole ring, pyrazole ring, thiazole ring, or thiadiazole ring.
The heterocyclic ring containing X1 may have one or more subtituents on the heterocyclic ring, and the substituent(s) on the heterocyclic ring may form a condensed ring through further condensation. In that case, the substituents on the heterocylic ring each is selected independently from alkyl group which may be substituted (e.g., alkyl group having 1 to 6 carbon atoms such as methyl group, ethyl group, or the like, carboxymethyl group, carboxyethyl group, trifluoroniethyl group, or the like), aryl group which may be substituted (preferably aryl group having 6 to 10 carbon atoms, e.g., phenyl group, naphthyl group, or the like), aralkyl group which may be substituted (benzyl group or the like, preferably aralkyl group having 7 to 10 carbon atoms in total), alkenyl group which may be substituted (e.g., vinyl group, 2-propenyl group, or the like), alkoxy group which may be substituted (preferably alkoxy group having 1 to 6 carbon atoms, e.g., methoxy group, ethoxy group, or the like), aryloxy group which may be substituted (e.g., phenoxy group, or the like), acyloxy group which may be substituted (preferably alkanoyloxy group having 2 to 7 carbon atoms such as acetyloxy group, benzoyloxy group, or the like), alkoxycarbonyl group which may be substituted (preferably alkoxycarbonyl group having 2 to 7 carbon atoms, e.g., methoxYcarbonyl, ethoxycarbonyl, or the like), aryloxycarbonyl group which may be substituted (e.g., phenoxycarbonyl group, naphthyloxycarbonyl group, or the like), carbamoyl group which may be substituted, acyl group which may be substituted (e.g., acyl group having 2 to 10 carbon atoms such as acetyl group, or the like), carboxyl group, hydroxyl group, cyano group, acylamino group which may be substituted (e.g., alkanoylamino group having 2 to 7 carbon atoms such as acetylamino group, benzoylamino group, or the like), nitro group, halogen atom (e.g., chlorine atom, bromine atom, fluorine atom, or the like), phosphono group, sulfo group, mercapto group, alkylthio group which may be substituted (e.g., allcylthio group having 1 to 6 carbon atoms such as methylthio group or ethylthio group, or the like), alkylsulfoxy group which may be substituted (e.g., alkylsulfoxyl group having 1 to 6 carbon atoms such as methylsulfoxy group or ethylsulfoxy group, or the like), alkylsulfonyl group which may be substituted (e.g., alkylsulfonyl group having 1 to 6 carbon atoms such as methylsulfonyl group or ethylsulfonyl group, or the like), and thiocyanato group.
Among them, a metal chelated dyestuff is preferred wherein, in the general formula (1), the heterocyclic ring containing X1 is preferably represented by the following general formula (5), (6), (7) or (8). 
(where R1 may be different from each other, is a group selected from alkyl group which may be substituted, aryl group which may be substituted, aralkyl group which may be substituted, alkoxy group which may be substituted, aryloxy group which may be substituted, acyloxy group which may be substituted, alkoxycarbonyl group which may be substituted, aryloxycarbonyl group which may be substituted, carboxyl group, carbamoyl group which may be substituted, hydroxyl group, acyl group which may be substituted, cyano group, acylamino group which may be substituted, nitro group, halogen atom, sulfo group, mercapto group, alkylthio group which may be substituted and thiocyanato group, R1 may further form a condensed ring together with an imidazole ring, c represents an integer of 0 to 2. R2 represents hydrogen atom, alkyl group which may be substituted, aryl group which may be substituted and allyl group which may be substituted.)
In particular, preferred is the case that R1 is an alkoxycarbonyl group which may be substituted, carboxyl group, or cyano group and preferred is the case that R2 is hydrogen atom or alkyl group which may be substituted. Most preferred is the case that c is 2, both of the two R1""s are cyano groups, and R2 is hydrogen atom or alkyl group which may be substituted. 
(where R3 may be different from each other and represents alkyl group which may be substituted, aryl group which may be substituted, aralkyl group which may be substituted, alkoxycarbonyl group which may be substituted, aryloxycarbonyl group which may be substituted, carboxyl group, carbamoyl group which may be substituted, hydroxyl group, cyano group or sulfo group, d represents an integer of 0 to 2. R4 represents hydrogen atom, alkyl group which may be substituted or aryl group which may be substituted.) 
(where R5 may be different from each other and represents alkyl group which may be substituted, aryl group which may be substituted, aralkyl group which may be substituted, alkoxy group which may be substituted, aryloxy group which may be substituted, acyloxy group which may be substituted, alkoxycarbonyl group which may be substituted, aryloxycarbonyl group which may be substituted, carboxyl group, hydroxyl group, acyl group which may be substituted, cyano group, acylamino group which may be substituted, nitro group, halogen atom, sulfo group, alkylthio group which may be substituted or arylthio group which may be substituted, and R5 may further form a condensed ring together with thiazole ring, e represents an integer of 0 to 2.)
Preferred are the case that R5 is alkyl group which may be substituted, the case that e=0 and R5 is absent, or the case that R5 forms a condensed ring together with thiazole ring. 
(where R6 represents hydrogen atom, alkyl group which may be substituted, aryl group which may be substituted, aralkyl group which may be substituted, mercapto group, alkylthio group which may be substituted, alkylsulfoxy group which may be substituted or alkylsulfonyl group which may be substituted.)
R6 is preferably hydrogen atom or alkyl group which may be substituted.
Among the heterocyclic rings represented by the above general formula (5), (6), (7) or (8), preferred is imdazole ring represented by the general formula (5).
Moreover, Ar1 in the general formula (1) is naphthyl group represented by the general formula (2), (3) or (4), and Y1 is a chelating group. Y1 is preferably hydroxyl group, carboxyl group, amino group which may be substituted (e.g., amino group, methylaniino group, bis(2-hydroxyethyl)amino group, or the like), sulfo group, carbanioyl group, alkoxy group which may be substituted (e.g., methoxy group, 2-hydroxyethoxy group, or the like), allcylthio group which may be substituted (e.g., methylthio group, 2-hydroxyethylthio group, or the like), alkylsulfonylamino group which may be substituted (e.g., methylsulfonylaniino group or the like), or arylsulfonylamino group which may substituted (e.g., benzenesulfonylamino group or the like). More preferred is the case that Y1 is hydroxyl group.
It is preferable that Z1 in the general formulae (2) to (4), each is independently a group selected from alkoxy group which may be substituted (e.g., alkoxy group having 1 to 6 carbon atoms such as methoxy group or ethoxy group, or the like), aryloxy group which may be substituted (e.g., phenoxy group, or the like), acyloxy group which may be substituted (e.g., alkanoyloxy group having 2 to 7 carbon atoms such as acetyloxy group, benzoyloxy group, or the like), alkoxycarbonyl group which may be substituted (e.g., alkoxycarbonyl group having 2 to 7 carbon atoms such as methoxycarbonyl, ethoxycarbonyl, or the like), aryloxycarbonyl group which may be substituted (e.g., phenoxycarbonyl group, naphthyloxycarbonyl group, or the like), carboxyl group, carbamoyl group which may be substituted (e.g., carbamoyl group or the like, carboxyanilide group which may be substituted (3-sulfocarboxyanilide group or the like), hydroxyl group, amino group which may be substituted (e.g., amino group, alkylamino group having 1 to 6 carbon atoms such as methylamino group, or the like), ureido group, acylamino group which may be substituted (e.g., alkanoylamino group having 2 to 7 carbon atoms such as acetylamino group, benzoylamino group, or the like), alkylsulfonylamino group which may be substituted (e.g., alkylsulfonylamino group having 1 to 6 carbon atoms such as methylsulfonylamino group, or the like), arylsulfonylamino group which may be substituted (e.g., phenylsulfonylamino group, 4-methylphenylsulfonylamino group, or the like), phosphono group, sulfo group, and sulfamoyl group which may be substituted (e.g., sulfamoyl group, N,N-bis(carboxymethyl)sulfamoyl group, or the like), a represents an integer of 0 to 6.
Z1 is preferably carboxyl group, carbamoyl group which may be substituted, sulfo group, or sulfamoyl group which may be substituted. a is preferably an integer of 1 to 3, more preferably 1 or 2.
Furthermore, among the naphthyl groups represented by the general formula (2), (3) or (4), preferred is the general formula (2) or (4).
In particular, most preferred is the naphthyl group of the following general formula (4xe2x80x2). 
(where R2xe2x80x3 represents sulfo group or sulfamoyl group which may be substituted.)
The azo compound represented by the general formula (1) is a compound having at least one hydrophilic group in a molecule other than Y1 which is a chelating group. Examples of such hydrophilic group include sulfo group, carboxyl group, hydroxyl group, amino group, phosphono group, or the like. Of these, preferred is sulfo group or carboxyl group. It is more preferable that the azo compound represented by the general formula (1) is a compound having 1 to 3 sulfo groups or carboxyl groups in a molecule
In the invention, examples of the metal forming a chelated compound together with the azo compound represented by the general formula (1) include silver (I), aluminum (III), gold (III), cerium (III, IV), cobalt (II, III), chromium (III), copper (I, II), europium (III) iron (II, III), gallium (III), germanium (IV), indium (III), lanthanum (III), manganese (II), nickel (II), palladium (II), platinum (II, IV), rhodium (II, III), ruthenium (II, III, IV), scandium (III), silicon (IV) samarium (III), titanium (IV), uranium (IV), zinc (II), zirconium (IV), and the like.
Preferred are nickel (II), cobalt (II, III), and copper (II). More preferred are nickel (II) and copper (II), and most preferred is nickel (II).
As an anion of the metal salt to be used at the production of the metal complex, a monovalent or divalent anion such as Clxe2x88x92, Brxe2x88x92, CH3COOxe2x88x92, SO42xe2x88x92, or the like may be mentioned.
The dyestuff for use in the invention may be used in a form of free acid, as it is, and when the dyestuff is formed as a salt form at the production, it may be used as it is, or may be converted to a desired salt form. Furthermore, a dyestuff wherein part of the acid groups is a salt form or a mixture of a salt-form dyestuff and a free acid-from dyestuff may be used. Examples of such salt form includes salts with alkali metals such as Na, Li, K, etc.; ammonium salts which may be substituted with alkyl group(s) or hydroxyalkyl group(s); or salts with organic amines. Examples of the organic amines include lower alkylamines, hydroxy-substituted lower alkylamines, carboxy-substituted lower alkylamines and polyamines having 2 to 10 alkyleneimine units having 2 to 4 carbon atoms, and the like. In these salt-form cases, the dyestuff is not limited to one kind of form and two or more kinds may be mixed.
Moreover, in the structure of the dyestuff for use in the invention, when two or more acid groups are contained in one molecule thereof, the two or more acid groups are salt forms or acid forms and may be different from each other.
As specific examples of the dyestuff include the dyestuffs having structures shown in following Table 1 to Table 6, but the invention is not limited thereto.
The azo metal chelated compound which is a water soluble dyestuff of the invention can be produced from an azo compound represented by the general formula (1) and a metal compound.
The azo compound represented by the general formula (1) is obtained according to a known method.
(Method A) Diazo Coupling Method
A method which comprises the diazotization of the following compound: 
and coupling with Hxe2x80x94Ar1. Alternatively (Method B), the compound is obtained according to the method condensing a hydrazino compound with a 1,2-naphthoquinone derivative. 
The water soluble azo metal chelated compound which is a compound of the invention can be produced by reacting the resulting azo dyestuff of the general formula (1) with a metal compound (e.g., NiCl2.6H2O, CuCl2.2H2O, or the like).
As the content of the water soluble dyestuff which is an azo chelated compound of the azo compound of the above general formula (1) with a metal in the recording liquid, the content of a deep color ink is preferably from 0.5 to 5% by weight, particularly from 2 to 4.5% by weight in total, relative to the total amount of the recording liquid. In the case that a pale color ink is used, the content of the dyestuff is preferably from 0.1 to 2% by weight, more preferably 0.1 to 1.5% by weight.
Moreover, the aqueous medium for use in the invention preferably contains water and, as a water soluble organic solvent, ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol (weight average molecular weight: about 190 to 400), glycerol, N-methylpyrrolidone, N-ethylpyrrolidone, 1,3-dimethylimidazolidinone, thiodiethanol, dimethyl sulfoxide, ethylene glycol monoallyl ether, ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, 2-pyrrolidone, sulfolane, ethyl alcohol, isopropanol, or the like, for example. These water soluble organic solvents are used usually in the range of 1 to 45% by weight relative to the total amount of the recording liquid. On the other hand, water is used in an amount of 50 to 95% by weight relative to the total amount of the recording liquid.
The quick-drying property and print quality after printing can be further improved by adding, to the recording liquid of the invention, 0.1 to 10% by weight, preferably 0.5 to 5% by weight of a compound selected from urea, thiourea, biuret, and semicarbazide relative to the total amount of the recording liquid or by adding 0.001 to 5% by weight of a surfactant relative to the total amount of the recording liquid.